This invention relates to a reflection type optical device utilizing an integration mirror or a segmented mirror for evenly distributing energy of a laser beam.
In this field of art, it is well known that an optical device of the type described above may comprise an optical integration mirror prepared by arranging a plurality of plane segment mirrors, each having a small rectangular surface area, one by one so as to provide a concave mirror surface as a whole. Also well known is an optical device that includes one plane mirror arranged in combination with the concave integration mirror mentioned above.
In the conventional optical device of the type described above, the respective plane segment mirrors are prepared and arranged so that the laser beams reflected by the respective segment mirrors are focused on corresponding respective points. Moreover, it is difficult to substantially eliminate an adverse diffraction effect caused on the boundary portions of the respective plane segment mirrors. Accordingly, when these conventional relfection type optical device are used, the energy of the laser beam is not evenly distributed as a heat source on a working point of a material to be worked, and for example, in an ordinal surface heat treatment, a quenching operation is not evenly carried out. In addition, since the area of the rectangular working point to be heated is limited in accordance with the size of each plane segment mirror, it is hard to change the size of the heat source for the material to be worked.